Biological ‘lure and kill’ system for bean weevils shows promise

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A biological control system for beetle pests of peas and beans would reduce the need for blanket insecticide application and help to reduce the issues with resistance.

Trials by PGRO at the Beeswax Farming Stubton Estate, near Newark include a ‘lure and kill’ trial. This is investigating the use of a naturally occurring fungus to control pea and bean weevil and, potentially, bruchid beetle. Currently, the main insecticides available to UK pulse growers for control of both pests are pyrethroids – and there is now evidence of partial resistance developing in pea and bean weevil populations.

In the plots, insects are attracted into inoculation stations using pheromones and exposed to the fungus so that they leave and transfer the spores to their fellow beetles. Field cages help retain a captive weevil population.

If successful, the development of this more targeted approach to pest control with the potential to reduce broadcast pyrethroid applications, will offer a more environmentally friendly option for growers.

There are many different pyrethroid products each with their own range of target pests in many different crops. Despite increasing issues with resistance in a number of target species they are still an important product for growers to control a wide range of pests.

Control of pea and bean weevil using pyrethroids in some regions is still good and another aspect of this project is to look at the efficacy of using the pyretroid in an alternative formulation – Entostat® which may provide resistance busting control.

Lure and kill

Early results from the second year replicated cage trials were conducted at PGRO and Rothamsted Research Ltd and although not statistically significant data were promising, suggested some control over weevil numbers. Data from the year 3 trials will be available shortly.

The principle benefits of the “Lure and Kill” system is that it employs a naturally occurring entomopathogen and targets the pea and bean weevil more specifically using an aggregation pheromone via an inoculation station. In this way it is hoped that fewer non-target species will be affected such as with broadcast insecticides.

The beetle pests will be lured to simple devices, baited with specific attractive odours, where they will be coated with spores of an insect fungal disease. When they leave the device they will spread the disease to other beetles. This will reduce pest beetle numbers and damage to the crops, but, unlike insecticide sprays, will not affect the environment or other beneficial and non-target insects such as pollinating bees.

Environmentally friendly

The insect fungal disease occurs naturally in the soil in the UK and does not pose a risk to other animals. The attractants used are either insect produced (pheromone) or are odours produced by flowering peas and beans.

The spores and the attractants will be prepared in a novel formulation that is electrostatically charged and sticks to the beetles body, being passed on to other beetles.

The project is funded by the Technology Strategy Board through the Agri-Tech Catalyst program, BBSRC and the industrial partners PGRO, BASF, Oecos and Exosect.